METHODS AND APPARATUS 19 



When several analyses of the various forms, representing the dif- 

 ferent seasons of the year and as many lakes as possible, have been 

 obtained, the planktologist can then strike an average and obtain, with 

 a reasonable degree of accuracy, a factor, a food-value factor if you will, 

 for each form. This will serve as an index of the role played by the 

 different organisms in the annual crop of organic matter produced by 

 the plankton of a body of water. When such factors are established 

 for the various planktonts, not only will it be possible to study the 

 productivity of a lake by the numerical method, but it will also enable 

 one to consider all numerical studies that have been made in the past 

 from this same standpoint, which will add very greatly to the value of 

 such studies. In brief, it will put the problem of plankton production 

 on a chemical and gravimetric basis ; that is, on the same basis as the 

 modern investigations with respect to the crop production of the land. 



